The principal objective of this research is to explore various hypotheses concerning speech production and perception processes and the relationship of language to the brain in language dissolution. Thai, a tone language in Southeast Asia, is the language chosen for investigation. A series of production and perception experiments are proposed to determine the nature and extent of speech production and perception deficits in Thai-speaking aphasics. These experiments are specifically designed to explore (1) voice-onset time, (2) tone, (3) vowel duration, and (4) rhythm. Data from these experiments are to be brought to bear on theoretical questions concerning the relationship of language to brain pathology, the mechanisms underlying phonemic and phonetic disintegration, the relationship between production and perception deficits, the dissociation of prosodic features, and the relationship between language dissolution and acquisition.